1. Field of the Invention
The present invention relates to an engine control method.
2. Description of the Related Art
Japanese Laid-Open Patent Publication 10-288070 discloses a technique for controlling the amount of fuel injection in a diesel engine. In this technique, the fuel injection is controlled so that the rotational speed of the engine is maintained at a targeted numerical value. This speed is maintained even when a load is applied to the engine (such as that of an accessory such as an air conditioner or a power steering system). An idling state may be detected based on the output of a switch. The switch detects the fully closed position of an accelerator. The fuel injection amount is corrected based on the input conditions of various parameters such that the rotational speed of the engine in its idling state is maintained at a fixed value. Any error in the fuel injection amount can be calculated based on the deviation between the corrected fuel injection amount and the actual amount of fuel injection. In this technique, the fuel injection amount in an operational range other than the idling state may also be corrected.
In the above-mentioned conventional technique, however, a correction amount of fuel injection amount is calculated only during an idling state, and the correction amount is decided based on map data which is predetermined using measurements from other operating conditions. Accordingly, the correction amount is not sufficient for use in an operational range outside of the idling phase. Particularly, the difference between a command value of corrected fuel injection and an actual amount of fuel injection is large at the time of transition during engine operation. Accordingly the air/fuel ratio largely deviates from a target air/fuel ratio and thus deteriorates the exhaust gas. Accordingly, there is a need for an engine control method where the difference between a control command value and an actual control value can be detected in an operational range outside of an idling state.